The Pediatric Oncology Group (POG) member institutions' collaborative research efforts are providing important information concerning the biology and treatment of most types of pediatric leukemias and solid tumors. Multidisciplinary participation in the cooperative studies and in the administrative and scientific activities of the POG forms the foundation for the University of Mississippi Medical Center's (UMC) clinical and laboratory research programs in pediatric oncology. The UMC is the only center in Mississippi providing comprehensive cancer care for the children of the state. UMC's POG affiliate institution, the USAF Medical Center Keesler, makes available specialized pediatric oncology care for children of military personnel from Mississippi and surrounding states. During the next grant period, the UMC principal investigator (PI) will serve as the POG New Acute Lymphocytic Leukemia (ALL) Committee's associate chair and as the chair of the New ALL Reference Laboratory Directors' Committee. The UMC has served as the coordinating institution for each of the POG's sequential New ALL laboratory classification studies and will coordinate the POG 9400 ALinC 16 classification protocol during the next grant period. These classification studies are defining specific biologic subgroups of ALL and demonstrating prognostic and pharmacologic differences among the subgroups. Patients are routed through the classification study to specially designed treatment protocols for B-Precursor, T-ALL, and B-ALL, respectively. Other biologic characteristics, such as cytogenetic findings and DNA Index, are combined with the traditional age/WBC factors in determining risk group and treatment protocol for patients with B-Precursor ALL. The UMC study coordinator's office assimilates all POG reference laboratory and local institution classification data in time for its use in treatment assignment. The Keesler affiliate PI participates in the planning and coordination of the POG's SIMAL studies for patients with relapsed ALL.